PROJECT SUMMARY/ABSTRACT Clinical type 1 diabetes (T1D) is preceded by an asymptomatic phase of the disease, which can be readily identified by serum islet autoantibodies(AAb). However, the T1D field is challenged by the lack of potent predictive markers, particularly ?-cell specific serum markers that can accurately predict and reveal the rate of T1D progression. The markers of such are critical in the development of novel and effective interventions for T1D. Therefore, the overall objective of this application is to establish ?-cell specific serum proteomic signatures that can predict the immunogenic progression of T1D. Our specific hypothesis is that the ongoing autoimmune destruction of ?-cells during the pre-T1D phase sheds ?-cell-specific protein signatures into the blood stream, and these circulatory signatures are suitable biomarkers for assessing ?-cell mass, predicting the trajectory of ?-cell destruction and thus the developmental stage of T1D. To pursue this objective, our rationale is to apply a hypothesis-focused integrative discovery approach to comprehensively identify putative ?-cell specific proteins, isoforms, and posttranslational modifications (PTMs) from pancreatic islets and tissues. Protein candidates are then prioritized and validated in the serum samples collected from large-scale longitudinal clinical studies such as the Diabetes Prevention Trial (DPT-1) via the implementation of an ultrasensitive targeted proteomic technology. The availability of a set of islet-specific proteins (already identified through our preliminary studies) and the unique ultrasensitive technology provides us a first-rate opportunity to establish novel predictive serum markers for T1D development. In our experimental plan, Aim 1 will focus on the integrative discovery of putative ?-cell specific proteins, isoforms, and PTMs by comparing pre-T1D versus control pancreas and islets. Aim 2 will conduct an initial screening for the top 100-200 candidates based on their detectability in human serum as well as their significant differential serum concentration in new-onset T1D subjects versus controls. Aim 3 will perform targeted validation of the most promising 10-30 candidates in the serum samples longitudinally collected in the DPT-1 cohort. The comparison will include three groups of subjects: 1) T1D relatives who had multiple AAb and progressed to T1D 2) T1D relatives who had multiple AAb but did not progress to T1D, and 3) AAb negative controls. We anticipate this application will enable us for the first time to successfully develop a panel of ?-cell specific serum markers, which will have a profound clinical implication for predicting T1D progression, assessing ?-cell mass, and monitoring the treatment efficacy.